smalloc.c

   1 /*
   2  * simple memory allocator, backed by mmap() so that it hands out memory
   3  * that can be shared across processes and threads
   4  */
   5 #include <sys/mman.h>
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <assert.h>
   9 #include <string.h>
  10 #include <unistd.h>
  11 #include <sys/types.h>
  12 #include <limits.h>
  13
  14 #include "mutex.h"
  15
  16 #undef ENABLE_RESIZE            /* define to enable pool resizing */
  17 #define MP_SAFE                 /* define to made allocator thread safe */
  18
  19 #define INITIAL_SIZE    1048576 /* new pool size */
  20 #define MAX_POOLS       32      /* maximum number of pools to setup */
  21
  22 unsigned int smalloc_pool_size = INITIAL_SIZE;
  23
  24 #ifdef ENABLE_RESIZE
  25 #define MAX_SIZE        8 * smalloc_pool_size
  26 static unsigned int resize_error;
  27 #endif
  28
  29 struct pool {
  30         struct fio_mutex *lock;                 /* protects this pool */
  31         void *map;                              /* map of blocks */
  32         void *last;                             /* next free block hint */
  33         unsigned int size;                      /* size of pool */
  34         unsigned int room;                      /* size left in pool */
  35         unsigned int largest_block;             /* largest block free */
  36         unsigned int free_since_compact;        /* sfree() since compact() */
  37         int fd;                                 /* memory backing fd */
  38         char file[PATH_MAX];                    /* filename for fd */
  39 };
  40
  41 static struct pool mp[MAX_POOLS];
  42 static unsigned int nr_pools;
  43 static unsigned int last_pool;
  44 static struct fio_mutex *lock;
  45
  46 struct mem_hdr {
  47         unsigned int size;
  48 };
  49
  50 static inline void pool_lock(struct pool *pool)
  51 {
  52         if (pool->lock)
  53                 fio_mutex_down(pool->lock);
  54 }
  55
  56 static inline void pool_unlock(struct pool *pool)
  57 {
  58         if (pool->lock)
  59                 fio_mutex_up(pool->lock);
  60 }
  61
  62 static inline void global_read_lock(void)
  63 {
  64         if (lock)
  65                 fio_mutex_down_read(lock);
  66 }
  67
  68 static inline void global_read_unlock(void)
  69 {
  70         if (lock)
  71                 fio_mutex_up_read(lock);
  72 }
  73
  74 static inline void global_write_lock(void)
  75 {
  76         if (lock)
  77                 fio_mutex_down_write(lock);
  78 }
  79
  80 static inline void global_write_unlock(void)
  81 {
  82         if (lock)
  83                 fio_mutex_up_write(lock);
  84 }
  85
  86 #define hdr_free(hdr)           ((hdr)->size & 0x80000000)
  87 #define hdr_size(hdr)           ((hdr)->size & ~0x80000000)
  88 #define hdr_mark_free(hdr)      ((hdr)->size |= 0x80000000)
  89
  90 static inline int ptr_valid(struct pool *pool, void *ptr)
  91 {
  92         return (ptr >= pool->map) && (ptr < pool->map + pool->size);
  93 }
  94
  95 static inline int __hdr_valid(struct pool *pool, struct mem_hdr *hdr,
  96                               unsigned int size)
  97 {
  98         return ptr_valid(pool, hdr) && ptr_valid(pool, (void *) hdr + size - 1);
  99 }
 100
 101 static inline int hdr_valid(struct pool *pool, struct mem_hdr *hdr)
 102 {
 103         return __hdr_valid(pool, hdr, hdr_size(hdr));
 104 }
 105
 106 static inline int region_free(struct mem_hdr *hdr)
 107 {
 108         return hdr_free(hdr) || (!hdr_free(hdr) && !hdr_size(hdr));
 109 }
 110
 111 static inline struct mem_hdr *__hdr_nxt(struct pool *pool, struct mem_hdr *hdr,
 112                                         unsigned int size)
 113 {
 114         struct mem_hdr *nxt = (void *) hdr + size + sizeof(*hdr);
 115
 116         if (__hdr_valid(pool, nxt, size))
 117                 return nxt;
 118
 119         return NULL;
 120 }
 121
 122 static inline struct mem_hdr *hdr_nxt(struct pool *pool, struct mem_hdr *hdr)
 123 {
 124         return __hdr_nxt(pool, hdr, hdr_size(hdr));
 125 }
 126
 127 static void merge(struct pool *pool, struct mem_hdr *hdr, struct mem_hdr *nxt)
 128 {
 129         unsigned int hfree = hdr_free(hdr);
 130         unsigned int nfree = hdr_free(nxt);
 131
 132         hdr->size = hdr_size(hdr) + hdr_size(nxt) + sizeof(*nxt);
 133         nxt->size = 0;
 134
 135         if (hfree)
 136                 hdr_mark_free(hdr);
 137         if (nfree)
 138                 hdr_mark_free(nxt);
 139
 140         if (pool->last == nxt)
 141                 pool->last = hdr;
 142 }
 143
 144 static int combine(struct pool *pool, struct mem_hdr *prv, struct mem_hdr *hdr)
 145 {
 146         if (prv && hdr_free(prv) && hdr_free(hdr)) {
 147                 merge(pool, prv, hdr);
 148                 return 1;
 149         }
 150
 151         return 0;
 152 }
 153
 154 static int compact_pool(struct pool *pool)
 155 {
 156         struct mem_hdr *hdr = pool->map, *nxt;
 157         unsigned int compacted = 0;
 158
 159         if (pool->free_since_compact < 50)
 160                 return 1;
 161
 162         while (hdr) {
 163                 nxt = hdr_nxt(pool, hdr);
 164                 if (!nxt)
 165                         break;
 166                 if (hdr_free(nxt) && hdr_free(hdr)) {
 167                         merge(pool, hdr, nxt);
 168                         compacted++;
 169                         continue;
 170                 }
 171                 hdr = hdr_nxt(pool, hdr);
 172         }
 173
 174         pool->free_since_compact = 0;
 175         return !!compacted;
 176 }
 177
 178 static int resize_pool(struct pool *pool)
 179 {
 180 #ifdef ENABLE_RESIZE
 181         unsigned int new_size = pool->size << 1;
 182         struct mem_hdr *hdr, *last_hdr;
 183         void *ptr;
 184
 185         if (new_size >= MAX_SIZE || resize_error)
 186                 return 1;
 187
 188         if (ftruncate(pool->fd, new_size) < 0)
 189                 goto fail;
 190
 191         ptr = mremap(pool->map, pool->size, new_size, 0);
 192         if (ptr == MAP_FAILED)
 193                 goto fail;
 194
 195         pool->map = ptr;
 196         hdr = pool;
 197         do {
 198                 last_hdr = hdr;
 199         } while ((hdr = hdr_nxt(hdr)) != NULL);
 200
 201         if (hdr_free(last_hdr)) {
 202                 last_hdr->size = hdr_size(last_hdr) + new_size - pool_size;
 203                 hdr_mark_free(last_hdr);
 204         } else {
 205                 struct mem_hdr *nxt;
 206
 207                 nxt = (void *) last_hdr + hdr_size(last_hdr) + sizeof(*hdr);
 208                 nxt->size = new_size - pool_size - sizeof(*hdr);
 209                 hdr_mark_free(nxt);
 210         }
 211
 212         pool_room += new_size - pool_size;
 213         pool_size = new_size;
 214         return 0;
 215 fail:
 216         perror("resize");
 217         resize_error = 1;
 218 #else
 219         return 1;
 220 #endif
 221 }
 222
 223 static int add_pool(struct pool *pool, unsigned int alloc_size)
 224 {
 225         struct mem_hdr *hdr;
 226         void *ptr;
 227         int fd;
 228
 229         strcpy(pool->file, "/tmp/.fio_smalloc.XXXXXX");
 230         fd = mkstemp(pool->file);
 231         if (fd < 0)
 232                 goto out_close;
 233
 234         if (alloc_size > smalloc_pool_size)
 235                 pool->size = alloc_size;
 236         else
 237                 pool->size = smalloc_pool_size;
 238
 239         if (ftruncate(fd, pool->size) < 0)
 240                 goto out_unlink;
 241
 242         ptr = mmap(NULL, pool->size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
 243         if (ptr == MAP_FAILED)
 244                 goto out_unlink;
 245
 246         memset(ptr, 0, pool->size);
 247         pool->map = pool->last = ptr;
 248
 249 #ifdef MP_SAFE
 250         pool->lock = fio_mutex_init(1);
 251         if (!pool->lock)
 252                 goto out_unlink;
 253 #endif
 254
 255         pool->fd = fd;
 256
 257         hdr = pool->map;
 258         pool->room = hdr->size = pool->size - sizeof(*hdr);
 259         pool->largest_block = pool->room;
 260         hdr_mark_free(hdr);
 261         global_write_lock();
 262         nr_pools++;
 263         global_write_unlock();
 264         return 0;
 265 out_unlink:
 266         if (pool->map)
 267                 munmap(pool->map, pool->size);
 268         unlink(pool->file);
 269 out_close:
 270         if (fd >= 0)
 271                 close(fd);
 272         return 1;
 273 }
 274
 275 void sinit(void)
 276 {
 277         int ret;
 278
 279 #ifdef MP_SAFE
 280         lock = fio_mutex_rw_init();
 281 #endif
 282         ret = add_pool(&mp[0], INITIAL_SIZE);
 283         assert(!ret);
 284 }
 285
 286 static void cleanup_pool(struct pool *pool)
 287 {
 288         unlink(pool->file);
 289         close(pool->fd);
 290         munmap(pool->map, pool->size);
 291
 292         if (pool->lock)
 293                 fio_mutex_remove(pool->lock);
 294 }
 295
 296 void scleanup(void)
 297 {
 298         unsigned int i;
 299
 300         for (i = 0; i < nr_pools; i++)
 301                 cleanup_pool(&mp[i]);
 302
 303         if (lock)
 304                 fio_mutex_remove(lock);
 305 }
 306
 307 static void sfree_pool(struct pool *pool, void *ptr)
 308 {
 309         struct mem_hdr *hdr, *nxt;
 310
 311         if (!ptr)
 312                 return;
 313
 314         assert(ptr_valid(pool, ptr));
 315
 316         pool_lock(pool);
 317         hdr = ptr - sizeof(*hdr);
 318         assert(!hdr_free(hdr));
 319         hdr_mark_free(hdr);
 320         pool->room -= hdr_size(hdr);
 321
 322         nxt = hdr_nxt(pool, hdr);
 323         if (nxt && hdr_free(nxt))
 324                 merge(pool, hdr, nxt);
 325
 326         if (hdr_size(hdr) > pool->largest_block)
 327                 pool->largest_block = hdr_size(hdr);
 328
 329         pool->free_since_compact++;
 330         pool_unlock(pool);
 331 }
 332
 333 void sfree(void *ptr)
 334 {
 335         struct pool *pool = NULL;
 336         unsigned int i;
 337
 338         global_read_lock();
 339
 340         for (i = 0; i < nr_pools; i++) {
 341                 if (ptr_valid(&mp[i], ptr)) {
 342                         pool = &mp[i];
 343                         break;
 344                 }
 345         }
 346
 347         global_read_unlock();
 348
 349         assert(pool);
 350         sfree_pool(pool, ptr);
 351 }
 352
 353 static void *smalloc_pool(struct pool *pool, unsigned int size)
 354 {
 355         struct mem_hdr *hdr, *prv;
 356         int did_restart = 0;
 357         void *ret;
 358
 359         /*
 360          * slight chance of race with sfree() here, but acceptable
 361          */
 362         if (!size || size > pool->room + sizeof(*hdr) ||
 363             ((size > pool->largest_block) && pool->largest_block))
 364                 return NULL;
 365
 366         pool_lock(pool);
 367 restart:
 368         hdr = pool->last;
 369         prv = NULL;
 370         do {
 371                 if (combine(pool, prv, hdr))
 372                         hdr = prv;
 373
 374                 if (hdr_free(hdr) && hdr_size(hdr) >= size)
 375                         break;
 376
 377                 prv = hdr;
 378         } while ((hdr = hdr_nxt(pool, hdr)) != NULL);
 379
 380         if (!hdr)
 381                 goto fail;
 382
 383         /*
 384          * more room, adjust next header if any
 385          */
 386         if (hdr_size(hdr) - size >= 2 * sizeof(*hdr)) {
 387                 struct mem_hdr *nxt = __hdr_nxt(pool, hdr, size);
 388
 389                 if (nxt) {
 390                         nxt->size = hdr_size(hdr) - size - sizeof(*hdr);
 391                         if (hdr_size(hdr) == pool->largest_block)
 392                                 pool->largest_block = hdr_size(nxt);
 393                         hdr_mark_free(nxt);
 394                 } else
 395                         size = hdr_size(hdr);
 396         } else
 397                 size = hdr_size(hdr);
 398
 399         if (size == hdr_size(hdr) && size == pool->largest_block)
 400                 pool->largest_block = 0;
 401
 402         /*
 403          * also clears free bit
 404          */
 405         hdr->size = size;
 406         pool->last = hdr_nxt(pool, hdr);
 407         if (!pool->last)
 408                 pool->last = pool->map;
 409         pool->room -= size;
 410         pool_unlock(pool);
 411
 412         ret = (void *) hdr + sizeof(*hdr);
 413         memset(ret, 0, size);
 414         return ret;
 415 fail:
 416         /*
 417          * if we fail to allocate, first compact the entries that we missed.
 418          * if that also fails, increase the size of the pool
 419          */
 420         ++did_restart;
 421         if (did_restart <= 1) {
 422                 if (!compact_pool(pool)) {
 423                         pool->last = pool->map;
 424                         goto restart;
 425                 }
 426         }
 427         ++did_restart;
 428         if (did_restart <= 2) {
 429                 if (!resize_pool(pool)) {
 430                         pool->last = pool->map;
 431                         goto restart;
 432                 }
 433         }
 434         pool_unlock(pool);
 435         return NULL;
 436 }
 437
 438 void *smalloc(unsigned int size)
 439 {
 440         unsigned int i;
 441
 442         global_read_lock();
 443         i = last_pool;
 444
 445         do {
 446                 for (; i < nr_pools; i++) {
 447                         void *ptr = smalloc_pool(&mp[i], size);
 448
 449                         if (ptr) {
 450                                 last_pool = i;
 451                                 global_read_unlock();
 452                                 return ptr;
 453                         }
 454                 }
 455                 if (last_pool) {
 456                         last_pool = 0;
 457                         continue;
 458                 }
 459
 460                 if (nr_pools + 1 >= MAX_POOLS)
 461                         break;
 462                 else {
 463                         i = nr_pools;
 464                         global_read_unlock();
 465                         if (add_pool(&mp[nr_pools], size))
 466                                 goto out;
 467                         global_read_lock();
 468                 }
 469         } while (1);
 470
 471         global_read_unlock();
 472 out:
 473         return NULL;
 474 }
 475
 476 char *smalloc_strdup(const char *str)
 477 {
 478         char *ptr;
 479
 480         ptr = smalloc(strlen(str) + 1);
 481         strcpy(ptr, str);
 482         return ptr;
 483 }